This invention relates to the bonding of rubber to metal.
Articles in which rubber is bonded to metal have been known for many years, and since the introduction of the steel-belted radial tyre, rubber/metal bonding has been very extensively studied. It it known that certain substances will act as adhesion promoters to improve the initial adhesion level between the rubber and the metal and the maintenance of the adhesion level during accelerated laboratory ageing tests designed to simulate conditions to which the article may be subjected during its service life.
The main adhesion promoters currently used to promote the bonding of brass-coated steel to rubber are cobalt compounds, for example cobalt naphthenate, and resorcinol-and/or melamine-formaldehyde resins used in conjunction with hydrated silica. Both of these types of adhesion promoters, which can be employed separately or in combination, have disadvantages, and alternative rubber/metal adhesion promoters to those currently employed are therefore desirable. Such alternatives are provided by the present invention.